broncobowsher
Contributor
The couple breaths after the air is off is a big one. Couple of breaths and watch the pressure is all it takes.
IF you check tank pressure and shut off the tank, depressurize the lines ALWAYS. Don't care if you purge a reg, fill a wing, just depressurize the lines. Same on open circuit as closed circuit.
As for a rebreather, you can get several minutes of breathing with the oxygen turned off. With the scrubber working you will have no CO2 rise, just a loss of O2. If starting with a rich mix in the rebreather you can get about a minute of oxygen per liter of counterlung volume. Now there will be protocol violations, and ignoring warning signs as well. Pool training involved turning the O2 off and watching what happens (in a pool, with instructor watching very carefully, one on one only). It is amazing how long it takes to burn off the O2 in a rebreather with the tank turned off.
IF you check tank pressure and shut off the tank, depressurize the lines ALWAYS. Don't care if you purge a reg, fill a wing, just depressurize the lines. Same on open circuit as closed circuit.
As for a rebreather, you can get several minutes of breathing with the oxygen turned off. With the scrubber working you will have no CO2 rise, just a loss of O2. If starting with a rich mix in the rebreather you can get about a minute of oxygen per liter of counterlung volume. Now there will be protocol violations, and ignoring warning signs as well. Pool training involved turning the O2 off and watching what happens (in a pool, with instructor watching very carefully, one on one only). It is amazing how long it takes to burn off the O2 in a rebreather with the tank turned off.